The fer de lance is one of the largest and deadliest of poisonous snakes. These venomous viper snakes can be fatal to humans.

The fer-de-lance is one of the largest and deadliest of poisonous snakes. These venomous viper snakes can be fatal to humans. They are nocturnal and can live over 20 years. The name, fer-de-lance, is French for "lance head." The Spanish know this snake as barba amarilla which means "yellow chin."

Fer-de-lances have large, speckled eyes with vertically elliptical pupils. They have brilles instead of eyelids which are transparent coverings over the eyes. The broad triangular head and the body are covered with gray or brown velvety scales. The average length of an adult fer-de-lance is 6 feet long.

These snakes are found in tropical rain forests and plantations in Central and South America. They live in wet and dry places, in forests and open country and are terrestrial. They live alone except when mating.

Fer-de-lances kill their prey, small mammals and birds, with their two front fangs. They twist their bodies into an S shape before striking. Two small holes, or pits, over their mounts are heat sensory organs. Fer-de-lances use these organs to find prey in their environment. Their forked tongues are chemically sensitive, meaning they can determine which chemicals are in their environment.

Mating year round, female fer-de-lances are viviparous, giving birth to live young. The gestation period is between 3 and 4 months, and they can give birth to up to 60 young. The babies can be up to one foot in length and have fully formed fangs with a poisonous bite. Young fer-de-lances may climb trees and survive on a diet of frogs and lizards by luring small mammals and birds with their yellow tipped tail.